The authoritative position of Lushan civil law textbooks has been maintained for 20 years, and the golden age of Lushan civil law will not last forever academically. The prosperity brought by the First World War promoted the rapid growth of Japan's economy, but with the end of the war, panic and economic depression flooded Japanese society, and the inherent contradictions of capitalism were also exposed. In the fields directly related to civil law, disputes arising from labor relations, tenant farmers' relations, and land and housing loans began to intensify. Coupled with the efforts of jurists to deal with this state of affairs and the unexpected interruption of the influence of German jurisprudence in the Great War, the criticism of German-style legal hermeneutics is getting stronger and stronger. Hideyoshi Muye, a professor of criminal law at Dongda University, threw out the theory of free law and was furious. "But it was the late Hong Yitaro who shook Hatoyama's civil law. He was the representative of the young German hermeneutics school that Hatoyama followed before. In the process of studying abroad, Mo Hong observed the turbulent European and American society and had a deep understanding. After returning home, he shouted: "German law is over!" On the one hand, he lashed out at the hermeneutics of civil law with external annotation as the standard and theoretical doubt as the function, and stressed the need to establish the hermeneutics of civil law with its own characteristics. As its initial work, it advocates a comprehensive study of precedents; On the other hand, we strongly advocate the establishment of a labor law with new theoretical factors, which is a typical social phenomenon that cannot be properly solved by the previous civil law theory. Yukio Hatoyama initially completed the great cause of Japanese civil law interpretation with the help of German school's legal interpretation. He was fed by great boredom and pain, and how to get rid of this boredom troubled him. Since then, Hatoyama has been extremely cautious and does not touch pen and ink easily. 19 10 published the introduction to the amendment of property law, and strongly advocated that the principles of individual ownership and freedom of contract can only be recognized if they are in line with social interests. Yukio Hatoyama, who has realized that change is the general trend, gave up the German hermeneutic literature he always loved. Referring to several theories on the basis of property rights, this paper is written in the spirit of opening up a new world. But in the end, Hatoyama still felt that "this thing is neither fish nor fowl" and that it is not in line with his own nature. After that, Yukio Hatoyama, as a member of the Japanese Committee of the League of Nations, lived in Europe for 1 year and 8 months. After returning to China, only one textbook, Introduction to Japanese Civil Law, was published (1923). Finally, the Creditor's Rights Law: The Principle of Good Faith was published in 1924. This paper strongly advocates that the contractual relationship should take the principle of good faith as the highest concept, and adjust and standardize the contractual relationship based on this principle. However, since then, I have never written an academic paper. 1926, 42-year-old Shan resigned from Professor Dongda and quit the academic circle, never to return.

Regarding Yukio Hatoyama's early resignation, my successor, my wife Rong, said that Mr. Wang wanted to give up the position of professor, but fundamentally speaking, Hatoyama, who ascended the throne of the second stage of Japanese civil law hermeneutics with "transaction safety", decided to fold the pen and accept the mountain after trying to change to the third stage. In this way, the hermeneutics of civil law was initiated by Mei Senjiro and Dong Yi Zheng Hong, and the successors Kawakami, Chaisaka and Yukio Hatoyama finally climbed the steep mountain explained by the Civil Code. Yukio Hatoyama, a successful climber, looks forward to the future of mountains and rivers. Although he tried to climb the second dangerous peak, he finally gave up and passed the baton to the third echelon player, my wife Rong. Hatoyama likes indoor entertainment, and both husband and wife love to play bridge. Yukio Hatoyama, who has a quick brain, often throws cards to discuss the outcome before he finishes playing, and the result is often as he said. Even now, among the legal scholars in Dongda University, bridge players are still excellent, which may be related to the tradition of that era, or the subtle hermeneutics has something in common with bridge. Hatoyama, in particular, is said to regard the law as a game. When Ishisaka was alive, he liked to fight it. After Ishisaka's death, Yukio Hatoyama complained: "The enemy is dead, even if you try hard, there is no goal." The death of rival Ishisaka is probably one of the reasons why Hatoyama ended his academic career ahead of schedule. If further consideration is given, for Hatoyama, who loves the game of German interpretation constructed by subtle theory, the new civil law dealing with social contradictions in the last years of Taisho (1925) has deviated from the correct rules of the game, which makes Hatoyama feel that this is not in line with his own nature. If Yukio Hatoyama can stay in the stage of long-term stability of capitalism, then Yukio Hatoyama, who has a smart and agile mind, will play the game of standardizing and interpreting laws all his life.

After retirement, Yukio Hatoyama spent the rest of his life as a lawyer, and was elected as a representative of Chiba Prefecture on 193 1. The Dictionary of Adult Names (Volume 5, page 184) and Yukio Hatoyama published by Japanese Pingfan Society recorded that "he was famous as a typical scholar and was ill in his later years". Half a year after the end of World War II, Yukio Hatoyama died in 0946 1 year at the age of 6 1 year.